Direct-current restorer system for color television receiver

ABSTRACT

1,000,064. Colour television receivers. RADIO CORPORATION OF AMERICA. Nov. 19, 1962 [Nov. 20, 1961], No. 43714/62. Heading H4F. The invention is concerned with the problem of D.C. restoration in a colour television receiver having a cathode-ray tube of the type in which the screen emits colour dependent upon the velocities of the exciting electrons impinging thereon from a plurality of electron guns, the cathodes of which are maintained at different potentials. Separate D.C. restorers are provided between the cathode of each gun and its associated control electrodes, the restorers being switched by variable amplitude pulses derived from an auxiliary source which pulses additionally control the brightness by way of adjustable amplitude line and frame blanking pulses which are added to the video signal. As shown in block form in Fig. 1 the video and synch. portion of the received composite signal is simultaneously applied to a plurality of circuits 28, 30, 32. The circuit 28 separates the chrominance sub-carrier signal which is then demodulated to produce &#34; X &#34; and &#34; Y &#34; colour components which are matrixed with the brightness signal in conventional manner in circuit 46. The brightness signal is obtained through first and second luminance amplifiers 30, 42. Circuit 32 separates the synch. pulses and in addition to these controlling the deflection coils 34, 92 they are also used to generate positive and negative pulses each derived from the horizontal flyback pulse. The negative pulse (at the terminal 104) controls the D.C. restorers 84, 86, 88 and in addition controls the brightness by way of circuit 90 which causes horizontal blanking pulses of adjustable amplitude to be added to the video signal in amplifier 30. Vertical blanking pulses are added via terminal 99. The positive pulse controls the screen rectifiers 78, 80, 82 which in turn supply the screen electrodes 56c, 58c, 60c. A further pulse derived from the synch. separator 32 triggers a high voltage generator 76 which produces the various voltages for the cathode-ray tube 36. As shown in the detailed circuitry of Fig. 2, video signals derived from the video amplifier of Fig. 1 are applied at the terminal 94 to the grid of the first luminance amplifier 96 together with the negative pulses derived at the terminal 104 from the horizontal flyback pulses. The negative pulses are, however, first passed through the neon tube 106 to prevent noise pick-up and are then added in the potential divider 110 (which comprises the brightness control on the receiver 1 to a pro-selected D.C. component. This arrangement ensures that the valve 96 is always driven well into the cut-off region (Fig. 3, a, b, c, and Fig. 4, not shown) during the blanking interval to provide a horizontal retrace blanking pulse in the luminance signal to eliminate noise on the received signal and to prevent brightening of the receiver screen during flyback. Similarly, vertical retrace blanking pulses are produced from the positive pulses derived from the vertical deflection coils applied to the cathode of the amplifier 96 via terminal 99. The modified luminance signal is applied to the second amplifier 114, the potential divider 118 acting as a &#34; contrast &#34; control for the receiver and is then applied in pre-selected portions to the three matrix amplifiers 146, 148, 150. The derived &#34; X &#34; and &#34; Y &#34; colour components of the received signal are applied at the terminals 186 and 188 respectively. Feedback of the colour signals B, G, R appearing at the anodes of the valves 146, 148, 150 to the anode of the luminance amplifier 114 is prevented by the isolating resistors 152, 156 and 160. The derived colour signals B, G, R are applied to the control electrodes of the respective guns 56, 58 and 60 through capacitors 48, 50 and 52. Connected between each control grid, for example 56b, and the cathode, for example 56a, is a D.C. restoring circuit comprising a diode 84a triggered by negative keying pulses from the terminal 104 to clamp the negative peaks of the blanking pulses in the signal applied to the control electrode 56b at a particular level with respect to the cathode. The level at which the diode clamps is determined by the potential divider 84d which is pre-set and the brightness of the picture is determined by the amplitudes of the blanking pulses relative to the characteristics of the gun, this amplitude being controlled by the previously mentioned potential divider 110. Thus at low amplitudes the blue signal is nearer the gun cut-off voltage than at high amplitudes resulting in a less bright picture. 78, 80 and 82 comprise the rectifier circuits for devising the screen voltages for the tube. An alternative restoring circuit comprising two diodes is also disclosed (Fig. 5, not shown). In this arrangement one diode is arranged to restore the blanking pulses to their correct level if they are too positive and the other diode restores the pulses if they are too negative. Provision is also made for adjusting the amplitudes of the screen voltages produced by rectifiers 78, 80, 82.

Sept. 13, i966 w. H. MoLEs ET AL 3,272,914

DIRECT-CURRENT RESTORER SYSTEM FOR COLOR TELEVISION RECEIVER Filed NOV. 20, 1961 5 Sheets-Sheet l DIRECT-CURRENT EESIORER SYSTEM FOR COLOR TELEVISION RECEIVER Filed Nov. 20, 1961 Sept 13, 1966 W H` MOLES ETAL 5 Sheets-Sheet 2 QQ- .@Qw.. ONA HWS I uw Sept. 13, 1966 W, H. MOLES ET AL 3,272,914

DIRECT-CURRENT RESIORER SYSTEM FOR COLOR TELEVISION RECEIVER Filed Nov. 20, 1961 5 Sheets-Sheet 5 3,272,914 DIRECT-CURRENT RESTORER SYSTEM FOR CLOR TELEVISION RECEIVER Warren H. Moles, Trenton, NJ., and Roland N. Rhodes, Levittown, Pa., assignors to Radio Corporation of America, a corporation of Delaware Filed Nov. 20, 1961, Ser. No. 153,287 9 Claims. (Cl. 178-5.4)

This invention relates to color television receivers, and more particularly to circuits for processing and supplying image representative 4signals to a color image display device in a color television receiver.

One type of color image display device that may be used in a color television receiver is a cathode ray tube having an image reproducing phosphor screen that emits light under electron'beam excitation, the color of the light being dependent upon the velocity of the electrons that excite the screen. This type of cathode ray tube may be called a penetration color tube, because the color of the light is dependent upon the depth to which the electrons penetrate into the screen before they are -stopped to cause light emission from the screen. The screen of a penetration color tube produces light of two or more primary colors when excited simultaneously by two or more electron beams, having diierent respective beam velocities so that each beam controls substantially only one of the colors that the screen may produce. Each electron beam is modulated in intensity with signals representative of the color that it is to control, and deflected horizontally and vertically to scan a raster on the tube screen in the usual manner in television receivers to produce a color light image.

In order to accelerate a plurality of separate electron beams in the same cathode ray tube to different velocities, it has been found practical to maintain the ultor or final accelerating anode of each of the separate electron guns that produce the beams at the same direct voltage, and to maintain the separate cathodes of the electron .guns at different direct voltages. By this means the electron beams from the plurality of electron guns are accelerated through different potentials and thus acquire different velocities. Using screens that provide three primary colors (blue, green, and red) having purity and brightness of commercial quality, it has been found that the difference in accelerating potentials for the three electron beams is on the order of several thousand volts.

The -radio frequency (RF) color television wave that is received and processed to display a color television image on any type of color image display device, includes, according to the present color television broadcasting standards, a composite color video signal that is amplitude modulated on a radio frequency (RF) picture carrier wave and an accompanying sound signal that is frequency modulated on a radio frequency (RF) sound carrier Wave. The picture and sound waves are spaced 4.5 mc. (megacycles) apart. The composite color video signal includes a luminance (monochrome or black and white) signal, a color subcarrier wave that is phase and amplitude modulated with signals representative of the hue and saturation of the colors of the image, and horizontal and vertical blanking intervals, within which scanning and color synchronizing information are included.

Present commercial color television receivers use the shadow mask type cathode ray color television tube as a color image display device. The shadow mask color television tube has three electron guns to provide three electron beams and each beam excites a separate color light emitting phosphor on the screen of the tube. The velocities of the three electron beams are substantially identical.

United States Patent O 3,272,914 Patented Sept. 13, 1966 lCC Color television receivers using a shadow mask color television tube generally separate the luminance `signal from the color subcarrier signal, and direct current (DC.) couple the luminance signal through luminance signal amplifiers between the video detector of the receiver and the cathodes of the three electron guns of the shadow mask color television tube. The color subcarrier Wave is demodulated to provide threeV separate colordil'erence signals that are alternating current (A.C.) coupled by capacitors to the control electrodes of the three electron guns. A color-difference signal is a signal that represents the difference between the luminance signal and a signal representative of one of the color components of the image, such as blue, green or red. The color-difference signals are combined with the luminance signal in the electron guns, themselves, to modulate the intensity of each of the electron beams in accordance with the color components of the image to be reproduced.

It will be apparent, however, that in a cathode ray tube in which the cathode potentials of the three electron guns are several kilovolts apart, such as in the operation in a penetration color tube, it would be impractial to D.C. couple the luminance signal to the cathodes, since the driving amplifiers would be subjected to high voltages, requiring the use of expensive electron tubes and circuitry.

In accordance with this invention, wherein the color television receiver uses as a color image display device a penetration color tube that has a plurality of electron guns, the cathodes of which are maintained at dilerent direct potentials, a composite color video signal is processed to derive a plurality of individual color signals representative of the intensities of the color components of the image to be reproduced. The color signals are capacitively coupled to the control electrodes of the electron guns of the penetration color tube. Direct current (D.C.) restoring circuits for the color signals are provided between the control electrodes and cathodes of the separate electron guns. In addition, means are provided to generate and apply other operating direct voltages to the electron guns which may be required for operation.

As previously noted, in a color television receiver using a shadow mask color television tube, the luminance signal is D.C. coupled through luminance signal ampliers to the cathodes of its electron guns. Manual control of the bias `or D.C. level of one of the luminance amplifiers may thus be used to control the image brightness. This type of brightness control cannot be used if D.C. coupling of the luminance signal is not used. In accordance with this invention, an auxiliary pulse signal is added to the color signals to provide a level in the color signals to which the D.C. restoring circuits may clamp the signal. The pulse is controllable in amplitude to serve as a brightness control. The auxiliary pulse signals are also used to provide horizontal and vertical blanking signals for the penetration color tube.

The invention may be further understood when the following detailed description is read in connection with the accompanying drawings in which:

FIGURE l is a block diagram of a color television receiver utilizing a penetra-tion color tube and including video signal processing circuits in accordance with the invention;

FIGURE 2 is a schematic circuit diagram of the signal processing circuits which may be used, in accordance with the invention, in the receiver shown in FIGURE 1;

FIGURES 3a-c and 4 are graphs showing curves illustrating certain operational characteristics of the circuits of FIGURE 2; and

FIGURE 5 is a modification of certain of the circuits shown in FIGURE 2 illustrating another embodiment of the invention.

The color television receiver represented in FIGURE 1 includes an antenna 10 lto intercept and supply a received RF co-lor television wave to a tune-r 12. The RF color television wave includes an RF picture carrier wave which is amplitude modulated with a composite color video signal and an RF sound carrier wave which is rfrequency modulated with a sound signal, spaced 4.5 megacycles from the RF picture wave, in accordance with present broadcasting standards. In the tuner 12, the received RF color television wave is heterodyned to an intermediate frequency (IF) wave (including an IF picture wave and an IF sound wave), which is applied to an IF amplifier 14 where it is amplified and supplied to a video detector 16 and an intercarrier sound detector 18.

The intercarrier sound detector 18 derives an intercarrier sound signal of 4.5 megacycles, frequency modulated with the sound signal, from the beat frequency between the IF picture wave and the IF sound wave. The intercarrier sound signal is applied from the intercar-rier sound detector 18 to a sound channel 20v where it is amplified, detected, and applied to a loudspeaker 22 to reproduce the sound represented by the sound signal carried as modulated to the originally received RF sound wave.

The composite color video signal is detected by the video detector 16 from the IF picture wave, and is applied to a video amplifier 24 where it is amplified and applied to several points in the receiver for further processing, i.e., to an automatic gain control (AGC) circuit 26, a bandpass amplifier 28, a first luminance amplifier 30 (through a luminance signal input terminal 94), and synchronizing and deflection circuits 32.

As is known, the AGC circuit 26 `generates a control voltage that is -responsive to the strength of the composite color video signal and supplies it to the tuner 12 and IF amplifie-r 14 of the receiver to control their respective gains. The synchronizing and deflection circuits 32 of the receiver generate signals that may be applied to an electromagnetic electron beam deflection yoke 34 surrounding the neck of a penetration color tube 36 to deflect the electron beams of the tube 36 to scan television rasters on a light emitting phosphor screen 38 of the tube 36 is synchronism with the synchronizing signals lof the composite video signal.

The first luminance amplifier 30 amplifies the luminance signal portion of the composite color video signal and applies it through a coupling capacitor 40 to a second luminance amplifier 42 rfor further amplification.

The bandpass amplifier 28 separates and amplifies the color subcarrier Wave and applies it to a color demodulator 44 which derives a pair of output signals representative of the color information contained in the color subcarrier wave.

The output signals from the color demodulator 44 and the luminance signal from the second luminance amplifier 42 are applied through terminals 186, 188 and 131, respectively, to a matrix-amplifier 46 which derives therefrom individual output components of the image, i.e. blue signals, green signals and red signals, available on the leads marked B, G and R, respectively. The blue, green and red signals are applied through coupling capacitors 48, 50 and 52, respectively, to the three electron guns of the penetration color tube 36.

The :luminance ampliers 30, 42, the bandpass amplifier 28, and the color demodulator 44 may be of the types that are presently used in commercial color television receivers using the shadow-mask type color television tube.

The penetration color tube 36 has an envelope 54 wi-thin which are included the llight emitting phosphor screen 38 and a trio of electron guns 56, 58 and 60. The first gun 56 will be hereinafter referred to as the blue gun; the second Igun 58 as the green gun; and the third gun 60 as the red gun. The screen 38 is o-f the type that emits light under electron excitation, the color of the light being dependent on the velocity of the exciting electrons. The screen 38 may be, for example, const-ructed in the manner specified in U.S. Patent No. 2,590,018, issued on March 18, 1952, lto L. R. Koller et al., and entitled, Production of Color Images.

The electron guns 56, 58, each contain, respectively, cathodes 56a, 58a, 60a; control electrodes 56h, 58h, 60h; screen electrodes 56e, 58e, 60C; focus electrodes 56d, 58d, 60d and acceleratng anodes 56e, 58e, 60e. The accelerating anodes 56e, 58e, 60e are electrically connected to a convergence `cage 62 (common to all three guns 56, 58, 60) which may be similar to the convergence cages presently used with the shadow mask color television tube, and includes individual magnetic pole pieces (not shown) associated with each electron gun 56, 58, 60, and arranged such that external magnetic fields may be applied through the envelope S4 to the pole pieces to control the position of each of the electron beams, individually. One ltype of convergence system that may be lused is shown, for example, in U.S. Patent No. 2,707,248, issued on April 26, 1955, to H. C. Goodrich, entitled Electromagnetic Beam-Convergence Systems for Tri-Color Kinescopes. While the electron lguns 56, 58, 60 are shown side-by-side for clarity of illustration, it is to be understood that they may be mounted in the tube in the same manner as in a shadow mask color television tube, i.e., each equidistant from a common axis and spaced apart by equal angles.

Positioned between the green gun 58 and the screen 38 is a first magnetic shield member 64 which serves to shield the electron beam emitted by the green gun 58 from the effect of a magnetic electron beam defiecting field applied to the tube 36 by the yoke 34 for a portion of the beam travel through the deliec-ting region of the tube 36. The defiectinig region is between the yguns 56, 58, 60 and the screen 38 and adjacent the guns 56, 58, 60, as will be explained in greater detail hereinafter. A second magnetic shield member 66, Ilonger than the first magnetic shield member 64, is positioned between the red gun 60 and the screen 38 so that the electron beam from the red gun 60 is shielded from the action of the beam defiecting field for a longer portion of its travel through the deflecting Aregion of the `tube 36 than is the green beam.

The convergence cage 62 is connected by contact strips 68, to a condu-ctive coating 72 on the inner surface of the envelope 54. The conductive coating 72 may be aquadag, which is used as an internal conductive coating in many present commercial black and white and shadow mask color Itelevision tubes. The conductive coating 72, is, in turn, connected to an aluminum backing 74 on the screen 38.

An accelerating voltage, (-1-) ultor voltage, is derived from high voltage circuits 76 for the receiver and applied through the envelope 54 to the conductive coating 72. Thus, the conductive coating 72, the aluminum backing 74, the accelerating anodes 56e, 58e, 60e, the convergence cage 62, and the magnetic shield members 64 and 66 are maintained at the ultor voltage.

The high voltage circuits 76 for generation of the ultor voltage may be of the well known flyback type in which high voltages are generated by rectification of hori- Zontal retrace or fiyback pulses from the horizontal output transformer of television receiver horizontal electron beam defiection systems. I'In addition, a positive high voltage, (-1-) HV voltage, and a negative high voltage, HV voltage, both less in absolute value than the ult-or voltage, are available from the high voltage circuit 76 and may also be generated by a fiyback type circuit. The HV voltage is applied to the cathode 56a of the blue gun 56 and the HV voltage is applied to the cathode 60a of the red gun 60. The cathode 58a of the green gun is connected to ground (that is, a point of reference potential) for the receiver. The total accelerating voltage for the blue gun 56 is the sum of the absolute values of the HV voltage and the (-1-) ultor voltage; the accelerating voltage for the green gun 58 is equal to the (-1) ultor voltage; and the accelerating voltage for the red gun is equal to the dierence between the absolute values of the (-1-) ultor voltage Iand the (-1) HV voltage.

Also available from the high voltage circuits 76 are three direct focus voltages, positive with respect to ground, which are labeled Focus B, Focus G and Focus R. The Focus B voltage is applied to the focus electrode 56d of the blue gun 56, the Focus G voltage is applied to the focus electrode 58d of the green gun 58, and the Focus R voltage is applied to the focus electrode 60d of the red gun 60. The focus voltages, as is known, maintain the electron beams from the electron guns 56, 58, 60 properly shaped.

Screen voltages for the screen electrodes 56C, 58C, 60C of the electron guns 56, 5S, 60 are derived by three screen rectifiers 78, 80, 82 connected, respectively, between the cathodes 56a, 58a, 60a and screen electrodes 56C, 58C, 60C. A positive voltage pulse, (-1-) pulse signal, derived from the horizontal fiyback pulse during the horizontal blanking interval appearing in the synchronizing and defiection circuits 32 is applied through a pulse terminal 194 to the screen rectifiers 78, 80, 82 to provide signal for rectification to the direct voltages required.

In order to bias the control electrodes 56b, 58h, 60b,

l0f the electron guns 56, 58, 60, three direct current (D C.) Irestorers 84, 86, 88 are connected, respectively, between the cathodes 56a, 58a, 60a and the control grids 56h, 58h, 60b. The D C. restorers 84, 86, 88 are keyed by a negative voltage pulse, pulse signal, applied through a pulse terminal 104, derived from the horizontal fiyback lpulses appearing in the synchronizing and defiection circuits 32 to set the voltage level of the negative-most portion iof the color signals from the matrixamplifier 46 which are coupled through coupling capacitors 48, 50, 52, respectively, and across the D.C. restorers 84, 86, 88 to the control electrodes 56h, 58b, 60b, respectively.

A brightness control circuit 90 is connected to the first luminance amplifier 30 and receives as an input signal the pulse signal derived from the synchronizing and defiection circuits 32. The circuitry and operation of the brightness control circuit 90 will be described hereinafter.

In order to deflect the electron beams from the electron guns 56, 58, 60 to scan television rasters on the screen 38, the electromagnetic deflection yoke 34, surrounding the neck of the tube 36 is driven by defiection signals from the synchroniz-ing and defiection circuits 32 to provide a time Varying magnetic field in the `defiecting region of the tube 36, that is, in the space immediately adjacent the guns 56, 58, 60 through which the electron beams fro-rn the guns must traverse to strike the screen 38. The amount of deflection imparted to an electron beam is directly proportional to the strength of the magnetic field and the length of field through which the beam must pass, and inversely proportional to the square root of the velocity of the electrons. Thus, if three different velocity electron beams traversed the same magnetic field through the same distance in the deflecting region of the tube 36, they would be deflected by different amounts and would not strike the screen 38 at the same point, The blue beam which has the greatest velocity would not be deflected through as great an angle, by a given magnetic field, as would the red beam which has the least velocity. In like manner, the green beam would be deflected through a greater angle than the blue beam but not as great as the red beam, since it is traveling at a slower velocity then the blue beam although at a faster velocity than the red beam.

It is necessary, however, to insure that the electron beams converge at substantially the same point on the screen from all three guns 56, 58, 60 throughout all defiection angles, and it is for this reason that the magnetic shield members 64, 66 are used. The magnetic shield members 64, 66 are made of a magnetic material to prevent the defiecting field of the yoke 34 from affecting an electron beam while the beam is within the shield member. The first magnetic shield member 64 is made of a length such that the green beam is effectively within the defiecting region Io the tube 36 for a shorter distance than the blue bea-m so that it will receive essentially the same degree of deflection, by a particular magnetic field, as the blue beam. The second magnetic shield member 66 is longer than the first magnetic shield member 64 so that the red beam is effectively within the defiecting region of the tube 36 for a shorter distance than both the green and blue beams so that its degree of deflection will be substantially the same as that of the green and blue beams.

It will also be seen that, as in the shadow mask color television tube, the three electron beams originante from the spaced points within the tube, and in `order for the beams from the three guns 56, 58, 60 to strike the screen 38 at the same point, even after compensation for their varying velocities by the magnetic shield members 64, 66, some additional form of beam convergence action is necessary. The additional convergence action is supplied by convergenve signals which may be generated by the synchronizing and deflection circuits 32 in a known manner (see previously cited U.S. Patent N-o. 2,707,248) and applied to a convergence yoke 92, positioned on the outside of the envelope 54 of the tube 36 over the convergence cage 62, to .apply individual convergence magnetic fields to the electron beams through the convergence cage 62 to modify, independently, the positions of the individual electron beams so that they converge at all points on the rasters scanned on the screen 38.

Many of the circuits described in connection with the color television receiver of FIGURE l are presently known and used in television receivers using the shadow mask color television tube. FIGURE 2 shows specific circuitry which maybe used, in accordance with the invention, for the first and second luminance amplifiers 30, 42, the brightness control circuit 90, the matrix-amplifier 46, the D.C. restorers 84, 86, 88 and screen rectifiers 78, 80, 82.

In FIGURE 2 a negative-going video signal (available from the video amplifier 24 of FIGURE l) is applied to the luminance input terminal 94 of the first amplifier 30, which is Connected to the control grid of a first luminance amplifier tube 96, that has its cathode connected to ground for the receiver through a bias resistor 98, and its anode connected to a source of operating potential, -1-B, through a high frequency peaking coil and a first video load resistor 102. A negative-going video signal is one in which the synchronizing signals extend in a negative direction from the image signals.

The pulse signals (which may be derived from the horizontal fiyba'ck pulses and is available from the synchronizing and defiection circuits 32 shown in FIGURE 1) are applied to the control grid of the first luminance amplifier tube 96 through a pulse signal input terminal 104 and the series combination rof a neon tube 106 and an isolating resistor 108. The neon tube 106 serves to prevent any extraneous noise signals from being applied to the first luminance amplifier tube 96 between occurrences of the pulse signals. A brightness control potentiometer 110, having a pair of end terminals `and a variable tap 112, has one end terminal connected to the source of low voltage operating potential, -1-B, for the receiver; the other end terminal connected -to a source of negative operating potentials, B; and the variable tap 112 connected to the control grid of the first luminance lamplifier tube 96. The luminance signal is modified during the blanking interval by applying the pulse signals to insure that the first luminance amplifier tufbe 96 is always driven to anode current cutofi during the blanking interval of the luminance signals. The -cutting off of the rst luminance amplifier tube during the horizontal blanking interval provides a horizontal blanking pulse in the luminance signal to prevent brightening of the horizontal retrace lines on the screen 38 of the penetration color tube 36. As will be more fully explained hereinafter, the amplitude (or height) of the horizontal blanking pulses determines the brightness of the image reproduced by the receiver and the amplitude is controlled by the setting of the tap 112 on the brightness control potentiometer 110. The horizontal blanking pulse height control action is more easily understood by considering the waveforms shown in FIG- URES 3 and 4.

FIGURE 3a illustrates the luminance signal waveform 200 that is applied 4to the control grid of the first luminance amplifier 96 of FIGURE 2, and includes an image portion 202, a horizontal blanking interval 204, a synchronizing signal 206 and extraneous noise pulses 208. The pulse signal, also applied to the control grid, is illustrated as the waveform 210 in FIGURE 3b and occurs substantially coincident in time with the horizontal blanking interval 204 of the luminance signal 200. The sum of the luminance signal 200 of FIGURE 3a and the pulse signal 210 of FIGURE 3b is shown as a combined signal 212 in FIGURE 3c. Note that the synchronizing pulse 206 and the noise pulses 208 are at the extreme negative-going portions of the combined signal 212.

Referring now to FIGURE 4, the transfer characteristics of the first luminance amplifier tube 96 are shown as curve 214 in a plot of the grid voltage (eg) of the tube 96 against the anode current (ip). Two combined signals 212a and 212b, that have different direct voltage components which are otherwise identical to the combined signal 212 shown in FIGURE 3c, are shown plotted along the eg axis. Anode current cutoff of the first luminance amplifier 96 is shown by the intersection of the curve 214 with the eg axis. The negative going portions of both the combined signals 212er, 212b extend beyond anode current cutoff and any extraneous noise that may appear in the luminance signal during the horizontal blanking interval does not appear in the anode output current, as illustrated by anode current curves 216a, 21612 corresponding, respectively, to the combined signals 212a, 212b. The position of the combined signals 21251, 212b along the eg axis is determined by the direct voltage content of the signal. The composite color video signal (from which the luminance signal is derived) includes a direct voltage cornponent, and a further direct current component may be selectively added to or subtracted from the luminance signal in accordance with the position of the tap on the brightness potentiometer 110. Variation of the tap 112 on the potentiometer 110 varies the position of the composite signal on the eg axis, as shown by the two combined signals 212g and 212b in FIGURE 4. By this means, a modified luminance signal is obtained from the first luminance amplifier 96 that includes a horizontal blanking pulse portion, occurring during the horizontal blanking interval, having an amplitude that may be selected by positioning the tap 112 on the brightness potentiometer 110. The added pulse signal 210 of FIGURE 3b is made large to insure that the first luminance amplifier 96 is always driven beyond anode current cutoff by the combined signals 212:1 and 212b as shown in FIGURE 4. As will be explained in greater detail hereinafter, the D.C. restorers 84, 86, 88 clamp the peak of the horizontal blanking pulse of the luminance signal at current cutoff bias for the electron guns 56, 58, 60, and thus provide horizontal retrace blanking for the penetration color tube 36; and, the amplitude of the horizontal blanking pulses determine the intensity of the electron beams that are modulated yby the signals that are applied to the guns 56, 58, 60 and thus control the brightness of the image reproduced by the penetration color tube 36.

Vertical retrace blanking of the penetration color tube 36 cannot be performed by simply adding vertical pulses to the composite video signal, because the horizontal blanking pulses continue to occur during the vertical blanking interval and would thus add to and appear on the vertical pulses. The D.C. restorers 84, 86, 88 would then clamp on the horizontal blanking pulses, instead of the added vertical pulse, with the result that the electron guns 56, 58, 60 would be conducting current during the vertical blanking interval, except when a horizontal blanking pulse was occurring. Vertical retrace blanking may be performed, however, by cutting off the first luminance amplifier tube 96 in a manner similar to that used to generate the horizontal blanking pulses. A positive-going vertical pulse (from the vertical windings of the yoke 72 or from the usual vertical output tube in the receiver) is applied to the cathode of the rst luminance amplifier 96 through a vertical pulse terminal 99. The vertical pulse is made large enough to insure `that the first luminance amplifier tube 96 is cut off for the duration of the vertical pulse. The resultant vertical blanking pulses that appear in the anode circuit of the first luminance amplifier tube 96 thus do not include any horizontal blanking pulses and the D.C. restorers 84, 86, 88 clamp on the vertical blanking pulses to cut off current in the electron guns 56, 58, 60 during the vertical blanking interval. The setting of the tap 112 on the brightness control potentiometer also fixes the height of the vertical blanking pulses, because the setting detemines the grid bias of the first luminance amplifier tube 96 and thus fixes the voltage required to cut ofir anode current, whether the voltage is applied to the control grid (as with the pulse horizontal signal) or the cathode (as with the positive-going vertical pulse).

The amplified and modified luminance output signal from the first luminance amplifier 96 is applied from the junction of the peaking coil 100 and the first video load resistor 102 through the coupling capacitor 40 to the control grid of a second luminance amplifier tube 114. A grid return resistor 116 is connected between the control grid and ground for `the receiver, and the cathode is connected to ground through a cathode bias potentiometer 118 having a variable tap 120, which is also connected to ground through a large capacitor 122. Variation of the position of the tap 120 on the potentiometer 118 serves as a constrast control for the receiver, because the capacitor 122 may be positioned to bypass all or a portion of the potentiometer 118 and thus change the gain of the second luminance amplifier tube 114, by feedback across the potentiometer 118. The screen grid of the second luminance amplifier tube 114 is connected to the source of operating potential, -l-B, through a resistor-capacitor network 124, and the suppressor electrode is connected directly to the cathode. The anode of the tube 114 is connected to the source of operating potential, -l-B, through the series cornbination of a high frequency peaking circuit 126 (which consists of the parallel combination of the primary winding 128 of a transformer 130 and a resistor 132); a blue drive potentiometer 134 and a green drive potentiometer 136 connected in parallel; a resistor 138; and the secondary winding 140 of the transformer 130. Each of the potentiometers 134, 136 have adjustable taps 142, 144.

The luminance signal, including the added horizontal and vertical blanking pulses, is amplified by the second luminance amplifier tube 114 and is available at the end of the high frequency peaking circuit 126 remote from the anode of the tube 114 and is applied to three matrix amplifier tubes 146, 148 and 150, which are pentode type electron tubes. A portion of the luminance signal selected by the position of the variable tap 142 on the blue drive potentiometer 134 is applied through a first isolating resistor 152, shunted by a capacitor 154, to the anode of a first matrix amplifier tube 146. In like manner, a portion of the luminance signal -is applied from the variable tap 144 on the green drive potentiometer 136 through a second isolating resistor 156, shunted by a capacitor 158, to the anode of a second matrix amplifier tube 148. Finally, the full luminance signal, from the end of the high frequency peaking circuit 126 remote from the anode of the second luminance amplifier tube 114, is applied through a third isolating resistor 160, shunted by a capacitor 162, to the anode of the third matrix amplifier tube 150.

The cathodes of the three matrix amplifier tubes 146, 148, 150 are connected, respectively, through individual cathode resistors 164, 166, 168 and through a common cathode resistor 170 to ground for the reeciver. The control grids are connected, respectively, through grid resistors 172, 174, 176 to the common cathode resistor 170, and the suppressor grids are each connected directly to their respective cathodes. The anodes are connected individually through load resistors 178, 180, 182, respectively, to the source of operating potential, |B, and the screen grids are connected, in common, through a resistorcapacitor network 184 to the source of operating potential, +B. The control grid of the first matrix amplifier tube 146 is also connected to a first signal input terminal 186, and the control grid of the third matrix amplifier tube 150 is connected to a second signal input terminal 188. The control grid of the second matrix amplifier tube 148 is connected to ground for signal frequencies lthrough a capacitor 190.

The signals applied to the first and second signal input terminals 186, 188 are derived from the color demodulator 44 shown in FIGURE 1. The color demodulator 44 may be of the type described in U.S. Patent No. 2,830,112, issued to D. I-I. Pritchard on April 8, 1958, and entitled Color Television, .to derive, from the color subcarrier wave, color representative X and Z color difference signals. The X signal is applied to the first input terminal 186 and the Z signal is applied to the second input terminal 188. The matrix amplifier tubes 146, 148, 150 perform the function of the matrix adder described in the aforementioned Pritchard Patent 2,830,112, and there appears at the respective anodes of the matrix-amplifier tubes 146, 148, 150, as a result of the matrixing of the X and Z signals, color difference signals, i.e., a blue signal minus a luminance signal (B-Y), a green signal minus the luminance signal (G-Y), and a red signal minus the luminance signal (R-Y). The luminance signal (Y), including the added horizontal and vertical blanking pulses, is also applied to the anodes of the tubes 146, 148, 150 from the second luminance amplifier tube 114, as previously explained. The resultant signals at the individual anodes of the matrix-amplifier tubes 146, 148, 150 is the sum of the two signals appearing at the anodes, i.e., (B-YH-(Y) or the blue signal (B) at anode of the first tube 146, (G-YH-(Y) or the green signal (G) at anode of the second tube 148, and (R-Y)i-(Y) or the red signal at anode of the third tube 150. The blue, green, and red signals each contain the added horizontal and vertical blanking pulses of the luminance signal.

Because the color signals (B, G, and R) `appear individually at the anodes of the matrix-amplifier tubes 146, 148, 150, i-t is necessary to insure that the color sig-l nal from one matrix-amplifier tube does not feedback through the anode circuit of the second luminance amplier 114 to the control grids of the other matrix-amplifier tubes. The isolating resistors 152, 156, 160 reduce this undesired feedback. As an example, consider a luminance signal being conveyed `from the anode circuit of the second luminance amplifier 114 to the anode of the third matrix yamplifier 150. The luminance signal is developed across a voltage divider comprising the third isolating resistor 160 and the load resistor y182 of the tube 150. The third isolating resistor 160 is shunted by a capacitor 162 to match the stray capacitance from the anode to ground effectively shunting -the load resistor 182. Typical values for the components of the circuit are shown in FIGURE 2 of the drawing. The isolating resistor 160 is 10,000 ohms and the load resistor 182 is 39,000 ohms. Thus about 80% of Ithe luminance signal is applied to the anode of the tube 150.

The action towards a feedback signal in the opposite direction, that is, from the matrix-ampliiier tube 1150 of the second luminance amplifier anode circuit, is dilierent. The feedback signal is developed across a voltage divider comprising the third isolating resistor 160 and the irnpedance of the anode circuit of the second luminance amplifier tube 114. As can be seen from the circuit values shown in FIGURE 2 of the drawing, lthe impedance of the luminance .amplifier anode circuit presented to the third matrix amplifier tube 150 is approximately 1,700 ohms (resistors 138, 1,200 ohms, in series with the parallel combination of potentiometers 134, 136. 500 ohms). Thus only about 14% of the feedback signal appears in the luminance amplifier anode circuit. lFor all practical purposes, the to 14% ratio effectively isolates the luminance amplifier circuit from signals in the anode circuit of the third matrix .amplifier tube 150.

The isolating action between the anode circuit of the second luminance amplifier tube 114 and the iirst and second matrix-amplifier tubes 146, 148 is similar.

The blue signal available 4at the anode of theI first matrix-amplifier tube 146 is applied through the coupling capacitor 48 to the control grid 56b of the blue gun 56. Note that for the purposes of simplicity, only portions of the three electron guns 56, 58, 60 of the tube 36 in FIG- URE 1 have been shown in FIGURE 2. The cathode 56a of the blue gun 56 is connected to the HV Voltage, `as explained in connection with FIGURE 1, and bypassed -to ground at signal frequencies through a capacitor 192.

The D.C. restorer 84 (shown in block form in FIG- URE 1) comprises a diode 84a which has its anode connected to the control grid `56b and i-ts cathode connected through a resistor 84h to the cathode 56a of the blue gun 56. Keying pulses, which are the pulse signals available at the terminal 104, are developed across a keying pulse potentiometer 84e and a portion of each keying pulse is `applied from an adjustable tap 84d on the potentiometer 84e through a capaci-tor 84e to the cathode of the DC. restorer diode 84a.

The D.C. restorer 84, in operation, serves to clamp the negative going portions of the blue signal applied to the control electrode 56b of the electron gun 56 at a particular voltage level with respect to the cathode 56a. Specifically, the amplitude of the negative-going horizontal and vertical blanking pulses of the blue signal applied .to the control grid 56h Aare set, as previously explained, by the position of the tap 112 on the brightness potentiometer 110, and the D.C. restorer 84 clamps the peak of these pulses to the potential of the cathode of the `diode 84a. The cathode potential of the diode 84a is set by selecting a portion of the pulse signal that appears across the keying pulse potentiometer 84C and applying it through the adjustable tap 84d and the capacitor 84C to the cathode of the diode 84a. The only time that the diode 84a can conduct is during the keying pulse interval, and the negative-going horizontal and vertical blanking pulses of the blue signal -are prevented from going more positive than the amplitude of the negative keying pulse appearing on the cathode of the diode 84a by lthe conduction of the -diode 84a.

It will be seen that the amplitude of the horizontal and vertical blanking pulses of the blue signal determines the position of blue signal on the grid voltage-ultor current transfer characteristics of the blue gun 56. At low amplitudes of the pulse, the blue signal is nearer ultor current cutoff than it is at high amplitudes ofthe pulses. As a consequence, high amplitudes of the pulses produce a brighter image than low amplitudes of the pulses.

The brightness control circuit has an additional advantages, in that it provides a noise free level in the blue signal on which to effect the D.C. restoration. As is known, the D.C. restoration can be made to clamp on the peak of the synchronizing pulse 206 shown in FIGURE 3a. However, if noise pulses 208 occur during the clamping interval, the D.C. restorers 84, 86, 88 could set up on the noise pulses rather than the synchronizing pulse and give -an incorrect bias to the electron gun S6.

The screen rectifier 78 (shown in block form in FIG- URE l) includes a rectifier diode 78a having its anode connected through a coupling capacitor 78b to the (-1-) pulse signals (available as horizontal fiyback pulses from the synchronizing and defiection circuits 32 shown in FIGURE l) a-t a (-1-) pulse signal input terminal 194. The cathode of the rectifier diode 78a is connected to the cathode 56a of the blue gun 56 through -a load resistor 78e` shunted by a capacitor 78d. A rectified direct voltage is available at the cathode of the rectier diode 78a yand is connected directly to the screen electrode 56e of the blue gun 56.

A direct current return resistor 196 for both the D.C. restorer 84 and the screen rectifier 78 is connected directly between the screen electrode 56C and the control electrode 56b.

The D.C. restorers 86, 88 Iand lthe screen reotifiers 80, 82 connected to the green gun 58 and the red gun 60, respectively, are identical in structure and operation with respect to the green and red signals to those described in connection with the blue gun 56.

The alternating current (A.C.) coupling of the color signals to the control grids of the electron guns 56, 58, 60, through the coupling capacitors 48, 5), 52, together with the D.C. restoration, prevents color temperature drift of the reproduced image on the screen 38 of the tube 36, which may be possible with D.C. coupled signals. By color temperature is meant the mixture of colors (red, blue, and green) reproduced on the screen 38 of the tube 36 to provide a desired white color. In a D.C. coupled circuit, the D.C. levels determine the color temperature, and if one level should drift or change by a different amount than another, the color temperature of the light emitted by the screen 38 Would change.

The adjustment or set up procedure for the receiver is relatively simple. The screen voltage for each of the electron guns 56, 58, 60 remains fixed. With no signal present in the receiver, -the taps 84d, 86d, 88d on the keying pulse potentiometers 84C, 86C, 88C are adjusted so that each electron gun is set just at cathode cut ofi. This provides the so-called background adjustment. For proper color balance in the reproduced image, the reproduction of a white signal must be made of a mixture of all three colors in a fixed ratio, whether the system is reproducing the brightest white of which it is capable or whether it is making some shade of gray. This adjustment is made lwith a received signal present, which may be from a test generator. The white balance is adjusted by varying the position of the taps 142, 144 on the blue and green drive potentiometers 134, 136 in the anode circuit of the second luminance amplifier tube 114, until the desired white mixture is obtained. By these two adjustments, the grid voltage-ultor current transfer characteristics of e-ach of the electron guns 56, 58, 6) are matched at two points, that is, at the current cutoff point and at a highlight point, and the white balance of any point in between rem'ains substantially constant.

It may be desired to utilize a double diode D C. restorer between the control grids and the cathodes of the electron guns 56, 58, 60, instead of the single diode D.C. restorer shown in FIGURE 2, in order to fix the proper bias on the electron guns 56, 58, 60, regardless of whether the has its anode connected directly to the control grid 56b of the blue gun 56 and its cathode connected through a resistor 254 to the cathode 56a of the blue gun 56. The second diode 252 has its cathode connected directly to the control grid 56b of the blue gun 56 and its anode connected through a resistor-capacitor circuit, comprising a load resistor 256 shunted by a capacitor 258, to the cathode -56a of the blue gun 56. The blue signal, which is available from the matrix amplifier tubes 146, 148, 150, shown in the circuit of FIGURE 2, is coupled through the coupling capacitor 48 to the control grid 56h of the blue gun 56. A keying pulse for the operation of the D.C. restorer 84, which is Ithe pulse signal available at the terminal 164 of the circuit shown in FIGURE 2, is lapplied through a pulse coupling capacitor 266 to the junction of the cathode of the first diode 250 and the resistor 254.

In operation, the keying pulse conditions the D C. restorer 84 for operation. If the keying pulse is, for example, Volts in amplitude, the cathode of the first diode 250 will be pulsed to an :amplitude of 100 volts, and the anode of the second diode 252 `will be held continuously at approximately 100 volts by the parallel connected resistor 256 and capacitor 258. Thus, if the horizontal and vertical blanking pulses of the blue signal are more positive than 100 volts, the first diode 250 conducts to restore them to their proper level. If -the pulses are more negative than 100 volts, the second diode 252 conducts to restore them to their proper level. The proper bias between the control grid 5611 and cathode 56a of the blue gun 56 is thus maintained.

The screen rectifier 78 shown in FIGURE 5 is similar to that shown in FIGURE 2, except that the amplitude of the (-1-) pulse signal applied thereto for rectification is made variable by connecting -a (-1-) pulse signal potentiometer 262 across the (-1-) pulse signal input terminal 194 (of FIGURE 2) and connecting a screen rectifier diode 264 through a coupling capacitor 266 to an adjustable tap 268 on the potentiometer 262. The amplitude of the (-1-) pulse signal rectified by the screen rectifier diode 264 is adjustable and provides an adjustable direct voltage lacross the resistor-capacitor circuit 270 of the diode 264, which is applied directly to the screen grid 56e of the blue gun 56. A direct current return for the screen rectifier diode 264 is provided by a resistor 272 connected between the anode `of the diode 264 and the cathode 56a of the blue gun 56.

The D.C. restorer circuits 86, 88 and screen rectifiers 80, 82 for the green and red guns 58, 6i), respectively, are identical in structure and operation to those for the blue gun 56.

If the D.C. restorers and screen rectifiers shown in FIGURE 5 are used in place of those shown in FIGURE 3, the set up procedure described in connection with FIG- URE 3, is substantially the same, with the exception that the (-1-) pulse signal potentiometer 262 is adjusted to provide the anode current cutoff point in the electron guns instead of the keying pulse potentiometers of the FIGURE 2 circuit, which are not used in the FIGURE 5 circuit. The color balance adjustment is the same as that described in connection with FIGURE 2.

One problem may Iarise in connection with the circuit shown in FIGURE 5 if a manual chrominance or color gain control is used in the receiver. As is known, a manual chrominance control for the color signals may be provided by a manual gain control on the bandpass amplifier 28 shown in FIGURE l. If this control is adjusted to a point to introduce substantially more color into the reproduced image than was present in the received signal (that is, to provide substantially more overall receiver gain for the color signals than for the luminance signal), the color signals applied to the electron guns 56, 58, 60 may be driven into the blacker than black region, causing conduction of the second diode 252 in `the D.C. restore-r circuit 84 of FIGURE 5 during the image interval, to give an incorrect image on the screen 38 of the tube 36. In order to prevent such a situation, a portion of the pulse signal available at the terminal 194 (of FIGURE 2) may be applied to the input terminals 186 and 188 of the matrix amplitiers, shown in FIGURE 2, to add a lixed amount of pulse signal to the color signals (in addition to the adjustable horizontal and vertical blanking pulses) to insure that n setting of the manual chrominance control can be made to drive the color signals into a blacker than black region.

The Video signal processing circuits described herein for use with a penetration color tube provide means for driving the three electron guns of the tube, the cathodes of which are maintained at substantially diierent direct potentials, in a relatively simple circuit that provides convenient adjustments for both the brightness and color of the reproduced image on the screen of the penetration color tube.

What is claimed is:

l. In a color television receiver having a source of luminance signal, including vertical and horizontal blanking intervals, a luminance signal processing circuit, the combination comprising:

a cathode ray tube having a light emitting phosphor screen and a plurality of electron guns, each of said guns having at least a cathode and a control elec trode;

power supply means for said receiver to supply operating potentials to said cathode ray tube for maintaining the cathodes of said electron guns at substantially different direct operating potentials;

a luminance signal translating circuit having a signal input circuit and a signal output circuit;

means for applying said luminance signal from said source of luminance signal to the signal input circuit of said luminance signal translating circuit and to derive a luminance signal in the signal output circuit of said luminance signal translating circuit; source of first pulse signals occurring at the rate of the horizontal blanking intervals of said luminance signal;

means for applying said iirst pulse signals to said luminance signal translating circuit to prevent signal translation therethrough during the application of said rst pulse signals to incorporate into said luminance signal a first pulse portion occurring at the rate of said horizontal blanking intervals;

a source of second pulse signals occurring at the rate of lthe vertical blanking intervals of said luminance signal;

means for applying said second pulse signals to said luminance signal translating circuit 4to prevent signal translation therethrough during the occurrence of said second pulse signals to incorporate a second pulse portion into said luminance signal occurring at the rate of said vertical blanking intervals;

a plurality of signal coupling means for applying said luminance signal, including said iirst and second pulse portions, between the control electrodes and cathodes of the electron guns of said cathode ray tube; and

a plurality of direct current restoring means each connected individually lbetween said control electrode and the cathode of one of said electron guns of said cathode ray tube for providing a bias voltage between said control electrode and cathode of each of said electron guns and for clamping the peaks of the first and second pulse portions of said luminance signal at said bias voltage such that cathode current in said electron guns is cut off during the occurrence of said first and second pulse portions of said luminance signal.

2. In a color television receiver having a source of luminance signal, including vertical and horizontal blanking intervals, a luminance signal processing circuit, the combination comprising:

a cathode ray tube having a light emitting phosphor screen and a plurality of electron guns, each of said guns having at least a cathode and a control electrode;

power supply means for said receiver to supply operating potentials to said cathode ray tube for maintaining the cathodes of said electron guns at substantially different direct operating potentials;

a luminance signal translating circuit having a signal input circuit and a signal output circuit;

means for applying said luminance signal from said source of luminance signal to the signal input circuit of said luminance signal translating circuit and to derive a luminance signal in the signal output circuit of said luminance signal translating circuit; source of iirst pulse signals occurring at the rate of the horizontal blanking intervals of said luminance signal;

means for applying said iirst pulse signals to said luminance signal translating circuit to prevent signal translation therethrough during the application of said iirst pulse signals to incorporate into said luminance signal a first pulse portion occurring at the rate of said horizontal blanking intervals;

a source of second pulse signals occurring at the rate of the vertical blanking intervals of said luminance signal;

means for applying said second signals to said luminance signal translating circuit to prevent signal translation therethrough during the occurrence of said second pulse signals -to incorporate a second pulse portion into said luminance signal occurring at the rate of said vertical Iblanking intervals;

a plurality of signal coupling means for applying said luminance signal, including said irst and second pulse portions, between the control electrodes and cathodes of the electron guns of said cathode ray tube;

a plurality of direct current restoring means each connected individually between said control electrode and the cathode of one of said electron guns of said cathode ray tube for providing a bias voltage between said control electrode and cathode of each of said electron guns and for clamping the peaks of the first and second pulse portions of said luminance signal at said bias voltage such that cathode current in said electron guns is cut off during the occurrence of said iirst and second pulsed portions of said luminance signal;

adjustable brightness control means connected with said luminance signal translating circuit and responsive to said rst pulse signals for varying the voltage required to prevent signal translation through said luminance translating circuit to adjust the amplitude of the lirst and second pulse portions incorporated into the luminance signal to control the brightness of the image reproduced by said cathode ray tube.

3. In a 4color television receiver having a source Of luminance signal, including vertical and horizontal blanking intervals, and a source of dem-odulated color representative signals, the combination comprising:

a cathode ray tube having a light emit-ting phosphor screen and a plurality of electron guns, each of said guns having at least a cathode and a control electrode;

power supply means for said receiver to supply operating potentials to said cathode ray tube for maintaining the cathodes yof said electron guns at substantially dilferent direot operating potentials;

a luminance signal translating circuit having a signal input circuit and a signal output circuit;

means for applying said Iluminance signal from said source of luminance signal to the signal input circuit nance signal a rst pulse portion occurring at the rate of said horizontal blanking interval;

a source of second pulse signals occurring at the rate of the vertical blanking intervals of said luminance signals;

means for applying said second pulse signals to said luminance signal translating circuit to prevent signal translation therethrough during the occurrence of said second pulse signals to incorporate a second pulse portion into said luminance signal occurring said -`1rst pulse signals and to incorporate into said 10 luminance signal a first pulse porti-on occurring at at the rate of said vertical blanking intervals; the rate of said horizontal blanking interval; a matrix circuit;

a source of second pulse signals occurring at the rate means for aplying said luminance signal including said of the vertical blanking intervals of said luminous rst and second pulse portions from the signal outsignal; 15 put circuit of said luminance signal translating cirmeans for applying said sec-on-d pulse signals to said cuit and color representative signals from said source luminance signal translating circuit to prevent sig- `of demodulated color representative signals to said nal translation therethrough during the occurrence matrix circuit for deriving individual color signals of said second pulse signals to incorporate a second therefrom, each individual color signal being reprepulse portion into said luminance signal occurring 20 sentative of the Iintensity of one of the color comat the rate -of said vertical blankin-g intervals; ponents lof the image to be reproduced by said telea matrix circuit; vision receiver and each including first and second means for applying said luminance signal including pulse portions corresponding to the rst and second said rst and second pulse portions from the signal pulse portions of said luminance signal; output circuit of said luminance signal translating plurality of capacitance means for coupling said circuit and color representative signals from said color signals, including said rst and second pulse source Iof demodulated color representative signals portions, each individually t0 one of Said Control to said matrix circuit for deriving individual color eleCtI'OdeS Of the eleCtrOn guns 0f said Cathode ray signals therefrom, each individual color signal being tube; representative yof the intensity of one of the color a plurality of direct current restoring means connected Components of the image to be reproduced by said individually between the control grids and the cathtelevisi-on receiver and each including rst and sec- `Odes 0f each 0f said eleCtrOu guns 0f said Cathode ond pulse portions corresponding to the iirst and secray tube fOr PrOVlding a bias V'Oltage betWeel'l the ond pulse portions of said luminance signal; control electr-ode and cathode of each of said eleca plurality of capacitance means for coupling said tren guns and for Clamping the Peaks 0f the l'st and color signals, including said tirst and second pulse second pulse portions of said color signals at said portions, each individually t0 one of said Conn-01 bias voltage such that cathode current in said electron electrodes of the electron guns of said cathode ray guns is Cut Oil during the 'Occurrence 0f said first and tube; and second pulse portions of said color signals; and

a plurality of direct current restoring means connected 40 adjustable brightness enntrel means Connected With individually between the control grids and the cathsaid lunlinanee signal translating eireuit and resPOn `ode of each of said electron guns of said cathode ray siVe t0 Said llrst Pulse signals fOr Varying the VOltage tube for providing a bias voltage between the control required t0 Prevent signal translation tllrOugll said electrode and cath-ode of each of said electr-on guns luminance signal translating Circuit t0 adjust the ain' and for clamping the peaks of the rst and Second plitude of the rst and second pulse portions incorpulse portions of said color signals at said bias voltage such that cathode current in said electron guns is cut oit during the occurrence of said irst and sec-ond porated into the luminance signal and the color signals to control the brightness of the image reproduced by said cathode ray tube.

pulse portions of said color signals. 5. In a color television receiver having a source of 4. In a color television receiver having a source of luminance signal, including vertical and horizontal blankluminance signal, including vertical and horizontal blanking intervals, and a source of demodulated color repreing intervals, and a source of demodulated color representative signals, the combination comprising: sentative signals, the combination comprising: a cathode ray tube having a light emitting phosphor a CatllOde ray tube haVing a light emitting PllOsPhOr screen and a plurality of electron guns, each of said screen and a plurality '0f electron guns, eaell 0f said 55 guns having at least a cathode and a control elecguns having aft least a cathode and a control electrade; trOde; power supply means for said receiver to supply oper- POWel supply nreans fOr said reeeiVer t0 suPIly Oper ating potentials to said cathode ray ytube for mainating Potentials t0 said Cathode ray tube for rnain' taining the cathodes of said electron guns at subtaining the cathodes 0f said electron guns at substan' 60 stantially different direct operating potentials; any @gerept direct Operating Pftentlals; a luminance amplifier having a signal input circuit and a luminance signal translating circuit having a signal a signal Output circuit.

input circuit and a signal output circuit; Y means for applying said luminance signal from said means for appli-,mg Salil lummance-Slgna-l fromsaid Source of luminance Sima] to the sional in ut cir uit source of luminance signal to the signal input circuit e e p c of Said luminance amplier to develop an amplified of said luminance signal translating circuit and for deriving a luminance Signal from the Signal Output luminance signal in the signal output circuit of said circuit of said luminance signal translating circuit; lumman ampher;

a source of lirst pulse signals occurring at the rate of a source 0f iirst Pulse SlgnflS occurring at the r'ate of the horizontal blanking intervals of said luminance the horizontal blanking lnterVals 0f said luminance signal; signal;

means for applying said rst pulse signals to said lumimeans for applying said first Pulse signals t0 said lu nance signal translating circuit to prevent signal transminance amplifier in a polarity to cut off said luminance amplifier and prevent signal translation lation therethrough during the applicati-on of said rst pulse signals and to incorporate into said lumitherethrough during the application of said rst pulse 17 signals to incorporate into said amplified luminance signal a first pulse portion occurring at the rate of said horizontal blanking intervals; a source of second pulse signals occurring at the rate means for applying said second pulse signals -to said luminance amplifier .in a polarity to cut ofi said luminance amplier and prevent signal translation therethrough during the occurrence of said second of the vertical blanking intervals of said luminance pulse signals to incorporate a second pulse portion signal; in said amplified luminance signal occurring at the means for applying said second pulse signals to said rate of said vertical blanking intervals;

luminance amplifier in a polarity to cut off said a matrix circuit; luminance amplifier and prevent signal translation means for applying said amplified luminance signal therethrough during the occurrence of said second including said first and second pulse portions from pulse signals to incorporate a second pulse portion the signal output circuit of said luminance amplifier in said amplified luminance signal occurring at the and color representative signals from said source of rate of said vertical blanking intervals; demodulated color representative signals to said a matrix circuit; matrix circuit for deriving individual color signals means for applying said amplified luminance signal intherefrom, each individual color signal bei-ng reprecluding said first and .second pulse portions from the sentative of the intensity of one of the color comsignal output circuit of said luminance amplifier and Ponents of the image to be reproduced by said telecolor representative signals from said source of devision receiver and each including first and second modulated color representative .signals to said matrix pulse pOrtiOnS Corresponding t0 the rst and second circuit for deriving individual color signals there- Pulse Portions of seid amplified luminance Signal; from, each individual color signal being representaa plurality of capacitance means for coupling said tive of the intensity of one of the color components COlOr SignalS, including Said rSt and Second pulse of the image to be reproduced by said television re- Portions, eaell individually 'fo one of said Control ceiver and each including first tand second pulse poreleeilodes of tlle election guns 0f said Cathode ray tions corresponding to the first and second pulse tube; portions of Said amplified luminance signal; a plurality of direct current restoring means each cona plurality 0f Capacitance means for coupling said nected individually between the control electrode color signals, including said first and second pulse and the cathode of one of said electron guns of said portions, each individually -to one lof said control Cathode my tube for PfoViding a bias Voltage be' electrodes of the electron guns of Said cathode Tay tween the control electrode and cathode of each of tube; and said electron guns and for clam-ping the peaks of the a plurality of direct current restoring means each conllfsi and second Pulse Portions of said Coloi' signals nested individually between the conn-O1 electrode at said bias voltage such .that cathode current in said and the cathode 0f one 0f said electron guns of said electron guns is cut ofi during the occurrence of said cathode ray tube for providing a bias voltage befirst and second pulse portions of said color signals; tween the control electrodes and cathodes of each `of find said electron guns and for clamping the peaks of adjustable .brightness c ontrol means connected with the first and second pulse portions of said color sigseid luminance amplifier and resPOnSiVe io said first nals at said bias voltage such that cathode current 40 Pulse signals for Varying the Voltage reflillfed to out in said electron guns is cut off during the occurrence of said first and second pulse portions of said color signals.

6. In a color television receiver having a source of off said luminance amplifier to adjust the amplitude of the first and second pulse portions incorporated into the amplified luminance signal and the color signals to control the brightness of the image reproduced by said cathode ray tube.

7. In a color television receiver having a source of luminance signal, including vertical blanking intervals, and a source of demodulated color representative signals, the combination comprising:

luminance signal, including vertical and horizontal blanking intervals, and a source of demodulated color representative signals, the combination comprising:

a cathode ray tube having a light emitting phosphor screen and a plurality of electron guns, each of said guns having at least a cathode and a control eleca cathode ray tube having a light emitting phosphor trede; screen and a plurality of electron guns, each of said power Supply means for Said receiver to Supply Oper guns having at least a cathode and a control elecating potentials to said cathode ray tube for maintrode; taining the cathodes of said electron guns at subpower Sup p 15. means f or Sald recelver to Supply qper-at` stantially different direct operating potentials; ing Poltentlals to Said Cathode ray tube for mammina luminance amplifier having a signal input circuit and lpg the. cathodes. of Sad elictron gun? at Subs/tan' a signal Output circuit; tially dlfferent d1rect operatmg potent1als; means for applying said luminance signal from said a lumfnance amphier lum/mg a Slgnal Input wenn and source of luminance signal to the signal input cira Slgnal Outputflrculi; cuit of said luminance amplifier to develop an arnmeans for applymg Sald lumlnance signal from said plified luminance signal in the signal output `circuit scure? of luimnan Slgilal to the Slgnal Input cliclm of said luminance amplifier of s ald luminance amplifier to develop an amplified a source of first pulse signals occurring at the rate of uminance Slgnzllim the Slgnal Output clrcuit of Said the horizontal blank' t ummance ampl .eri Signal, mg m ervals of sald lummance a source of pulse slgnals occurring at the rate of the means for applying Said rst pulse Signals to Said 1u 65 vertical blanking 1n tervals of said luminance slgnal; minance amplifier in a polarity to cult Off Said 1u ymeans 1f'clr apply1ngsa1d`pulse signals to sald luminance minance amplifier and prevent signal translation ampller mda polanty tol Cut o-saldh lumman therethrough during the application of said first am? l er an prevent Slgna t-ranslauoni erethrough I durmg the occurrence of sa1d pulse signals to in- Pulse Sign? S t0 incorporate um? Said amPhed 1u' 70 corporate a pulse portion in said amplified luminance minance signal first Pulse Portion occurring at the signal occurring at the rate of said vertical blanking rate of sald horizontal blankmg interval; intervals; a source of second pulse signals voccurring at the rate a matrix circuit;

of the vertical blanking intervals of said luminance means for applying said amplified luminance signal insignal; Cludlng said pulse portion from the signal output lg circuit of said luminance ampliiier and color representative signals from said source of demodulated color representative signals to said matrix circuit for deriving individual color signals therefrom, each in- 20 A occurrence of said pulse portions of said color signals; and

adjustable brightness control means connected with said luminance amplifier for varying the voltage required dividual color signal being representative of the into cut olf said luminance amplitier to adjust the amtensity of one of the color components of the image plitude of the pulse portions incorporated into the to be reproduced by said television receiver and each amplified luminance signal and the color signals to including pulse portions corresponding to the pulse control the brightness of the image reproduced by portions of said amplied luminance signal; said cathode ray tube.

a plurality ot capacitance means tor coupling said 9. In a color television receiver having a source of color signals, including said pulse portions, each individually to one of said control electrodes of the electron gun of said cathode ray tube; and

luminance signal, including vertical and horizontal blanking intervals, and a source of demodulated color representative signals, the combination comprising:

a plurality of direct current restoring means each connected individually between the control grid and the cathode of one of said electron guns of said cathode ray tube for providing a bias voltage between the grid and cathode of each of said electron guns and for clamping the peaks of the pulse portions of said color signals at said bias voltage such that cathode current in said electron guns is cut olf during the occurrence of said pulse portions of said color signals.

8. In a color television receiver having a source of a cathode ray tube having alight emitting phosphor screen and a plurality of electron guns, each of said guns having at least a cathode, a screen electrode, and a control electrode;

power supply means for said receiver to supply op erating potentials t0 said cathode ray tube for maintaining the cathodes of said electron guns at substantially dilerent direct operating potentials;

a luminance signal translating circuit having a signal input circuit and a signal output circuit; means for applying said luminance signal from said source of luminance signal, including vertical blanking intervals, and a source of demodulated color representative signals, the combination comprising:

luminance signal to the signal input circuit of said luminance signal translating circuit and for deriving a luminance signal from the signal output circuit a cathode ray tube having a light emitting phosphor screen and a plurality of electron guns, each of said of said luminance signal translating circuit; a source of `irst pulse signals of both a positive and guus having at least a cathode and a control elec' 30 negative polarity occurring at the rate of the horitrcde; zontal blanking intervals of said luminance signal; PoWer suPPly means f or said receiver to supply O Perat means for applying said lirst pulse signals of a negaing Potentials to said cathode ray tube for maintain" tive polarity to said luminance signal translating ciring tue catliodes of said electron gurls at gunsten cuit to prevent signal translation therethrough durtrally different direct oPerating Potentials9- 35 ing the application of said first pulse signals and to a luminance ampliiler liaVing a signal input circuit and incorporate into said luminance signal a first pulse a Signal output circuit; portion occurring at the rate of said horizontal blankmeans for applying said luminance signal from said ing intervals;

source of luminance signal to the signal lnPut elr a source of second pulse signals occurring at the rate Cult 0f Said luminance amPliiier to deVeloP an arri" 40 of the vertical blanking intervals of said luminance plilied luminance signal in the signal output circuit Signal; 0f Said luminance amPlitier; means for applying said second pulse signals to said a Source of Pulse signals occurring at trie rate o t the luminance signal translating circuit to prevent sig- Vertical blanlting intervals oi said luminance signaii nal translation therethrough during the occurrence means f or aPPlYing saldpulse signals te sind luminance of said second pulse signals to incorporate a second amplifier in a Polarity to cut oir said luminance pulse portion into said luminance signal occurring amplier and prevent signal translation therethrough at the rate of said Vertieal blaiiking intervals; during the occurrence of said pulse signals to ina matrix eii-euil; c orPorate a P ulse Portion in said a'riiPlined luminance means for applying said luminance signal including said signal occurring at tlie rate of said Vertical ulanldng first and second pulse portions from the signal outmteryals put circuit of said luminance signal translating cira matrix circuiti cuit and color representative signals from said source means for applying said amphfied lummance slgnal in' of demodulated color representative signals to said cluding said Pulse Portion from the signal output matrix circuit for deriving individual color signals circuit or said luminance arnpllner and color rep' 55 therefrom, each individual color signal being representative signals from said source of demodulated resentative of the intensity of one of the color comcolor representative signals to said matrix circuit ponents of the image to be reproduced by Said telefor deriving individual color signals thereirom, each vision receiver `and each including iii-St and second individual color signal being representative of the puise portions correspoi-iding to the iirst and Second intensity of one of the color components of the 6o pulse portion of Said luminance Sigiial; image to lie reproduced by said television receiver a plurality of capacitance means for coupling said color and each including Pulse Portions corresponding to signals, including said iirst and second pulse por the Pulse Portions or Said alnPllned lurninanee Signal; tions, each individually to one of said control eleca plurality of capacitance means for coupling said C Olor trodes of the electron guns of said cathode ray tube; signals, including s aid Pulse Portions each iridiVid' 65 a plurality of direct current restoring means connected ually to one o f said control electrodes of tue elec' individually between the control grids and the cathtrOn gun 0f Sald cathode ray tube; odes of each of said electron guns of said cathode a plurality of direct current restoring means each conray tube for providing first direct operating voltages nected individually between the control grid and the between the control electrodes and cathodes of each cathode of one of said electron guns of said cathode of said electron guns and for clamping the peaks ray tube for providing a bias voltage between the of the rst and second pulse portions of said color grid and cathode of each of said electron guns and signals at said lirst direct operating voltage such for cla-mping the peaks of the pulse portions of said that cathode current in said electron guns is cut off color signals at said bias voltage such that cathode during the occurrence of said first and second pulse current in said electron guns is cut oli:` during the portions of said color signals;

21 22 adjustable brightness control means connected with said to vary the current cut oli bias for said electron luminance signal translating circuit and responsive guns.

to said rst pulse signals of negative polarity for varying the voltage required to prevent signal trans- References Cited by the Examiner lation through said luminance signal translating cr- 5 UNITED STATES PATENTS cuit to adjust the amplitude of the rst and second 2,965,705 12/1960 Luther 178 5 4 pulse portions incorporated into the luminance si-g- 2967Q62y 1/1961 ,Madey nal and the color signals to control the brightness 3,043,909 7/196t2 Loughlin l78-7.5

of the image reproduced by said cathode ray tube, 3,056,853 10/1962 Espenlaub 178-5.4

La plurality of rectifier circuit means each connected l0 3,059,140 10/ 19162 Heuer 3l5-l3 separately between the cathodes and screen electrodes 3,052,914 11/1962v Felnld et a1 178-5-4 0f each of Said electron guns; 3,113,237 liz/19163 SChOPp et al. 315--31 3,204,143 8/1965 Pritchard 198-5 .4

means lfor applying said first pulse signals of positive polarity to said plurality of rectifier circuit means 15 D AVID G. RBDINBAUGH, Primary Examiner. to develop second direct operating voltages on each of said screen electrodes; and ROB'IJRT SEGAL Exammer means for varying one of said direct operating voltages J. A. OBRIBN, Assistant Examiner. 

1. IN A COLOR TELEVISION RECEIVER HAVING A SOURCE OF LUMINANCE SIGNAL, INCLUDING VERTICAL AND HORIZONTAL BLANKING INTERVALS, A LUMINANCE SIGNAL PROCESSING CIRCUIT, THE COMBINATION COMPRISING: A CATHODE RAY TUBE HAVING A LIGHT EMITTING PHOSPHOR SCREEN AND A PLURALITY OF ELECTRON GUNS, EACH OF SAID GUNS HAVING AT LEAST A CATHODE AND A CONTROL ELECTRODE; POWER SUPPLY MEANS FOR SAID RECEIVER TO SUPPLY OPERATING POTENTIALS TO SAID CATHODE RAY TUBE FOR MAINTAININ THE CATHODES OF SAID ELECTRON GUNS AT SUBSTANTIALLY DIFFERENT DIRECT OPERATING POTENTIALS; A LUMINANCE SIGNAL TRANSLATING CIRCUIT HAVING A SIGNAL INPUT CIRCUIT AND A SIGNAL OUTPUT CIRCUIT; MEANS FOR APPLYING SAID LUMINANCE SIGNAL FROM SAID SOURCE OF LUMINANCE SIGNAL TO THE SIGNAL INPUT CIRCUIT OF SAID LUMINANCE SIGNAL TRANSLATING CIRCUIT AND TO DERIVE A LUMINANCE SIGNAL IN THE SIGNAL OUTPUT CIRCUIT OF SAID LUMINANCE SIGNAL TRANSLATING CIRCUIT; A SOURCE OF FIRST PULSE SIGNALS OCCURRING AT THE RATE OF THE HORIZONTAL BLANKING INTERVALS OF SAID LUMINANCE SIGNAL; MEANS FOR APPLYING SAID FIRST PULSE SIGNALS TO SAID LUMINANCE SIGNAL TRANSLATING CIRCUIT TO PREVENT SIGNAL TRANSLATION THERETHROUGH DURING THE APPLICATION OF SAID FIRST PULSE SIGNALS TO INCORPORATE INTO SAID LUMINANCE SIGNAL A FIRST PULSE PORTION OCCURRING AT THE RATE OF SAID HORIZONTAL BLANKING INTERVALS; A SOURCE OF SECOND PULSE SIGNALS OCCURRING AT THE RATE OF THE VERTICAL BLANKING INTERVALS OF SAID LUMINANCE SIGNAL; MEANS FOR APPLYING SAID SECOND PULSE SIGNALS TO SAID LUMINANCE SIGNAL TRANSLATING CIRCUIT TO PREVENT SIGNAL TRANSLATION THERETHROUGH DURING THE OCCURRENCE OF SAID SECOND PULSE SIGNALS TO INCORPORATE A SECOND PLUSE PORTION INTO SAID LUMINANCE SIGNAL OCCURING AT THE RATE OF SAID VERTICAL BLANKING INTERVALS; A PLURALITY OF SIGNAL COUPLING MEANS FOR APPLYING SAID LUMINANCE SIGNAL, INCLUDING SAID FIRST AND SECOND PULSE PORTIONS, BETWEEN THE CONTROL ELECTRODES AND CATHODES OF THE ELECTRON GUNS OF SAID CATHODE RAY TUBE; AND A PLURALITY OF DIRECT CURRENT RESTORING MEANS EACH CONNECTED INDIVIDUALLY BETWEEN SAID CONTROL ELECTRODE AND THE CATHODE OF ONE OF SAID ELECTRON GUNS OF SAID CATHODE RAY TUBE FOR PROVIDING A BIAS VOLTAGE BETWEEN SAID CONTROL ELECTRODE AND CATHODE OF EACH OF SAID ELECTRON GUNS AND FOR CLAMPING THE PEAKS OF THE FIRST AND SECOND PULSE PORTIONS OF SAID LUMINANCE SIGNAL AT SAID BIAS VOLTAGE SUCH THAT CATHODE CURRENT IN SAID ELECTRON GUNS IS CUT OFF DURING THE OCCURRENCE OF SAID FIRST AND SECOND PULSE PORTIONS OF SAID LUMINANCE SIGNAL. 